Feed device for thread grinding



July 26, 1960 K. H. sCHULTZE ETAL 2,946,161

FEED DEVICE FOR THREAD GRINDING MACHINES FEED DEVICE FOR THREAD GRINDINGMACHINES Kurt H. Schultze, Berlin-Frohnau, and Otto Jaeckel,Berlin-Tegel, Germany, assignors to Herbert Lindner GmbH.,Berlin-Wittenau, Germany Filed Feb. 25, 1958, Ser. No. 717,446

Claims priority, application Germany Apr. 17,I 1957 13 Claims. (Cl.51-165) This invention relates in general to feed devices for threadgrinding machines, and particularly to a new and useful automaticfeeding device for thread grinding machines, or the like, in which theadvance of the grinding mechanism is automatically controlled to apredetermined adjustable amount which may be varied for each of aplurality of successive grinding feed passes.

Previously, with machines of this general nature, automatic devices forhunting the grinding feed and hence the depth of grinding cut consistedof such mechanism as a pawl which rotated a ratchet over an adjustablenumber of peaks. Such devices were capable of effecting the same depthof cut for each feed or pass of the grinding wheel. It was not possiblewith these mechanisms, to vary the extent of grinding wheel feed fromone pass to the other.

In accordance with one aspect of the invention, an apparatus is providedto effect a variation in the extent of grinding wheel feed for eachsuccessive pass. With such a machine, it is possible to preselect thedepth of grinding for each successive pass as desired. The mechanismfinds particular application in thread grinding where it is particularlyadvantageous to make the first few grinding passes deep grinding cuts,and to make successive passes at gradually decreasing depth until thefinal precise size is reached.

Accordingly, it is an object of the present invention to provide anautomatic grinding wheel feeding device for thread grinding machines, orthe like, in which grinding feed is automatic and adjustable for eachsuccessive grinding pass.

A further object of the invention is to provide an apparatus forautomatic grinding wheel feeding, which includes control mechanismengageable with a stop to limit the extent of grinding wheel feed duringeach grinding pass, and which mechanism is effective to position a newstop in yalignment for contact to limit the extent of grinding wheelfeed during the succeeding grinding wheel feed pass.

A further object of the invention is to provide a grinding wheel feedingdevice which is simple in design, rugged in construction, and economicalto manufacture.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,its operating advantages and specific objects attained by its use,reference should be had to the accompanying drawings and descriptivematter in which there is illustrated and described a preferredembodiment of the invention.

In the drawings:

Fig. l is an overall schematic view of a thread grinding Wheel feedingdevice constructed in accordance with the invention; and

Fig. 2 is a front elevation of the feed drum indicated in Fig. 1 andtaken along the line 2--2 of Fig. l.

Referring to the drawings in particular, the invention as embodiedtherein includes a thread grinding wheel -1 atent 0 ICC which -isconstantly rotated by mechanism (not shown) to grind the surface of aslowly rotated work piece 2. The work piece 2 is supported on a carriageor table (not shown) to advance and retract the work piece axially ofthe grinding wheel 1. The grinding wheel 1 is supported in a movablefeed member or head stock 3.

A feed control screw spindle 4 is mounted in suitable bearings forrotation thereon and is provided with suitable mechanism such as asliding nut 4a which rides in a spiral groove thereon. The nut 4a issecured to the head stock 3 and movement of the head stock toward andaway from the work piece 2 is controlled by the rotation of the feedcontrol screw Spindle 4. Rotation of the feed control spindle 4 iseffective to control the depth of the grinding cut upon rotation of thespindle in one direction, and rotation of the spindle in the oppositedirection, is effective to return the grinding wheel 1 to its startingposition after each grinding cycle.

In accordance with the invention the amount of rotation of the feedcontrol spindle 4, and the extent of the advance of the grinding wheel 1during a cycle, is determined by a feed drum 5. The feed drum 5 isjournalled in bearings 6, 6 and is provided with a plurality ofsubstantially dovetailed cross-sectional grooves 7 which are uniformlyspaced around the circumference and extending the full length of thedrum 5. In this embodiment, six grooves are-provided to accommodatecontrol stop blocks 8 in each one thereof. A number greater, or less,than six could be advantageously provided, as determined by the numberof successive grinding wheel feed passes which must be controlled as tothe extent of feeding and the depth of grinding cut.

Some of the control stop blocks 8 are provided with feed stops 9 as theblocks 81, S2, 83 and 84, while two of the blocks are set for idling anddo not carry any stops as at 80, 80. In Fig. 1 of the drawings only twoof the control stop blocks 8 are indicated for clarity of illustrationpurposes. In this figure, blocks '82 and 83 should also normally appearin the grooves 7. In this embodiment correct grinding of thework piece 2requires four separate feed passes of the grinding wheel 1, and each ofthe passes are set to effect a different grinding depth. The arrangementpermits the grinding wheel to idle or to remain out of contact with thework piece during two cycles of operation of the control mechanism toaord time for the positioning of the next work piece.

The feed drum 5 is also provided with a plurality of annular grooves 71to permit adjustment of the location of each of the control stop blocks8. The annular grooves 71 intersect the longitudinal grooves 7 and theblocks 8 are shaped so that they can be set into the annular grooves andthen clamped tight in the longitudinal grooves. The feed stops 9 arethreaded and can be screwed into the control stop blocks 8 to aord alineadjustment of the stop location. The length of the threaded portion ofthe stop 9 is such that adjustment can be made to cover the rangebetween two positions of t-he coarse adjustment of the blocks in theannular grooves and longitudinal grooves.

The feed drum 5 is re-positioned once during each cycle of the controlmechanism to present a different control stop block in an operatingposition for the next control cycle. The feed drum 5 is indexed into a.precise position during each control cycle, by movement of a ratchetwheel 14 having six upstanding pins 13 annularly spaced on a concentriccircle thereon and which drives the feed drum 5 through the medium ofbevel gears l5 and 16. The bevel gear `16 is affixed to a shaft 17 whichis connected to the feed drum 5. The ratchet wheel 14 is rot-atedthrough engagement by a pawl `18' with the ypins 13. 'Ille pawl 18 ispivotally attached as at 19 to a push rod 21 which is axially guided forreciprocable movement in bearings 20. The push rod is biased downwardlyby a compression spring 22 which is positioned between an abutment onthe push rod 21 and the bearings 26.

The feed drum is indexed, that is, rotated-step by step, by thereciprocation ofthe pawl 1S as it engages the members 13 and `advancesthe reel 14. It essential that the drum 5 be held fast in each position.For this purpose, a detention disc 11 is provided which cooperates witha spring biased bolt 12 which is urged by the spring into one of aplurality of recesses defined in the disc l1. The flanks of the bolt 12are beveled -and so are the flanks of the recesses in the detention discand the bolt is urged out of the recess as the drum 5 is indexed to anew position. The rotational force exerted on the drum 5 causes movementof the bolt against the spring biasing force out of the recess in thedetention disc during each indexing movement.

When ya control stop 8 with its feed stop 9 is in an operating positionthe stop 9 faces the lower end 23 of the push rod 21, the lower end 23being spaced a distance from the top of the stop 9. Reciprocably movableinY this space is a double acting trip-dog 24, which Vis fixedly mountedon la control element or control rod 25. The control rod 25 is connectedat one end to a piston 26 and at its other end to a rack 27.

The piston 26 is reciprocable in a cylinder 28 having a cover 281 and abottom 282. The piston is acted upon by a hydraulic iiuid supplied by apump 29 and controlled by a slide valve 30. The extent of travel of thepiston 26 is determined by the point at which the stop 9 contacts thetrip-dog 24 in the lowermost position, yand by the point at which thepiston contacts the cover 281 in the uppermost position. In theembodiment shown, the cover 281 limits the upper movement of the piston26, however, any other stationary stop positioned either in the cylinder28 or outside of it would be suitable.

The slide valve 3d includes a horizontally reciprocable piston 31connected at its one end to a solenoid 32. The solenoid 32 is movablewithin and between two electromagnetic coils 33 and 34. Conduits 35 and36 lead 4from spaced central locations connecting the valve 30 to thecylinder 28, serving :alternately as a feed line and as a return line.The lines continue from the slide valve 30 to a sump 37 through conduits38 and 39.

A pressure sensitive switch 46) is `arranged -in the conduit 35 and isprovided with a spring biased piston 41 lin a cylinder 42, which isconnected to the conduit 35. The other end of the piston 41 is connectedto a contact 43 and movement of the piston 41 under increased pressurecauses the contact to complete an electrical circuit 44. The circuit `44is connected to the coil 33 of the solenoid 32. The other coil 34 of thesolenoid 32 is arranged in an electrical circuit 45. The circuit 45comprises a switch 46, such as a pulse switch, or a relay contact, whichis actuated either by the automatic control mechanism of the grindingmachine, or limit switches (not shown), connected with suitable elementsof the machine (for example, at each end of the carriage carrying thework piece), or by a hand adjustment to be described more fullyhereinafter. The main supply circuit of direct current is generallyindicated at 47.

The rack 27 of control rod 25 cooperates with a pinion 271 to rotate auelectromagnetic clutch 48 affixed to the same shaft as the pinion 271. Agear 49 operatively connected to one of the mating portions of theelectromagnetic clutch 48 is rotated thereby when the clutch iselectrically energized and rotated by movement of the rack 27. The gear49 meshes with a vgear 56 which in turn drives a gear 5l affixedV to thespindle 4 to rotate the latter. The gear 49 is also arranged to meshwith a small gear 52. An electromagnetic clutch 53, adapted kto couplewith a clutch engaging portion on a shaft 54, may be rotated when theclutch is actuated electrically, `by revolving -a hand wheel 55. The twoelectromagnetic clutches 48 and 53 are alternately energized by a twowayswitch 56. When the switch 56 is in the solid line position indicated inFig. l, the electromagnetic clutch 48 is energized for automatic feed.When the position ofthe switch S6 is inthe dotted line position theclutch 53 will be energized to draw the clutch mating .portion on theshaft 54 thereto, so that control is effected by manual operation of thehand wheel 55. Y

The operation of the thread grinding machine is as follows:

The grinding of the work piece 2 is accomplished when the spindle lisrotated to advance the grinding wheel 1 into an operative grindingposition therewith. After a traverse of the work piece 2, the switch 46is actuated, either by the automatic controls of the grinding machine,or directly by the movement of -a sliding table (not shown) whichsupports the work. When the switch 46 is energized the coil 34 of thesolenoid 32 is energized thereby and the piston 31 of the slide valve 30is moved into the position indicated by the dash lines. The pump 29directs fluid from the reservoir 38 through the conduit 35 and into thecylinder space below the piston 26. The piston 26 is moved upwardlyuntil it reaches the position indicated by the dash lines adjacent thecover 281.

The control rod 2S which is moved upwardly with the rack 27 causesrotation of the screw spindle 4 through the gear train 459, Si) and Si.The rotation of the screw spindle causes movement of the nut 4a in adirection away from the work piece to withdraw the head stock 3 fromengagement therewith.

Prior to the piston reaching its upper terminal position against thecover 231, the dog 24, which is aiiixed to the control rod Z5, willengage the push rod extension 23 of the push rod 21 to cause the pawl i8to engage an upstanding pin 13 of the ratchet wheel 14 to rotate theratchet wheel. The rotation of the ratchet wheel 14 causes rotation ofthe feed drum 5 to bring the next stop 9 of a feed block 8 into anoperative position. When the piston 26 reaches the upper-most positionindicated by the dash lines, the pressure behind the piston increases,to cause the pressure switch 4t) to energize the electrical circuit 44,and cause the coil 33 of the solenoid 32 to move the solenoid 32 to thefull line position and return the piston 31 to the full line positionindicated in Fig. l. In this position, the piston 31 directs fluid fromthe pump 29 through conduit 36 and into the cylinder 2S in the Spaceabove the piston 26. The piston is returned by the force of the uid toits lowermost terminal position indicated by the solid lines. Thelowermost position is determined by the feed stop 9 which limits thelower travel of the dog 24 aihxed to the control rod 25.

The downward movement of the piston 26 causes the feed spindle 4 torotate and move the nut 4a and the grinding wheel 1 toward the workpiece 2. The extent of this movement, and hence the depth of cut madeduring this grinding wheel pass, is adjusted and set by means of thestop 9. After a traverse of the work piece is completed, the Contact 46is actuated as previously and the cycle is repeated.

After the last traverse of the work piece 2, the switch is actuated bythe automatic control to maintain the grinding wheel away from the workpiece in an idle positioncorresponding to the idle settings 3D, S9. Forthe idling position, the stops 9 are set to hoid the grinding wheel wellclear of the work piece 2.

Thus the invention provides a simple mechanism for controlling the depthof cut ot a grinding wheel during each pass in a multi-pass grindingoperation. The mechanism provides for simpie depth cutting control toeffect a great many variations of cut for a plurality of individualgrinding cycles. The mechanism provides simple hand operation andcontrol if desired, as well as complete automatic grinding andcontrolled grinding depth stages.

While a specific embodiment of the invention has been shown anddescribed in detail to illustrate the application of the inventionprinciples it will be understood that the invention may be embodiedotherwise without departing from such principles.

What is claimed is:

l. A feed device for a thread grinding machine including means forsupporting a work piece, a grinding means mounted for movement towardand away from and laterally in respect to said work piece supportingmeans, means for moving said grinding means to and fro laterally, meansfor advancing said grinding means toward said work piece supportingmeans whereby to grind a work piece supported thereon during eachlateral feeding movement of said grinding means in one direction andaway from said work piece supporting means during lateral movement ofsaid grinding means in the opposite direction, means for controllingsaid advancing means, and means responsive to said controlling meansduring each grinding cycle to alter said controlling means and effectchange in the extent of movement of said advancing means towand saidwork piece supporting means during the next grinding cycle.

2. A Ifeed device according to claim l including a plurality of stopsmovable into and out of an operative position, a xed stop, and saidcontrolling means movable between said fixed stop and an operative oneof said movable stops during each grinding cycle to actuate saidadvancing means and simultaneously advance one of said movable stopsinto an operative position for the next grinding cycle.

3. A feed device according to claim 2 including a feed drum connected tosaid control means, said movable stops being positioned incircumferential and longitudinal offset positions on said feed drum, andsaid drum is rotated by said control means to move a stop into aneffective operating position for the next grinding cycle.

4. A feeding device according to claim 3 wherein said control meansincludes a control rod, a member aixed to said control rod and extendingoutwardly therefrom, said member being effective to engage an operativeone of said movable stops to limit the movement of said control rod andsaid grinding wheel advancing means.

5. A feeding device according to claim 4 including a piston at one endof said control rod, a cylinder in which said piston is movable, meansto move said piston to its uppermost position against said fixed stop,and means thereafter effective to move said piston downwardly.

6. A feeding device according to claim 5 wherein said means for movingsaid piston downwardly includes means for building up pressure in saidcylinder beneath said piston, and means responsive to said pressureincrease beneath said piston to cause said pressure means to be directedagainst the top of said piston and reduced below said piston.

7. A grindino wheel feeding device for thread grinding machinescomprising means for supporting a work piece, a constantly rotatinggrinding wheel, means for advancing said grinding wheel toward said workpiece supporting means and into operative association with a work piecesupported thereby, a feed drum, a plurality of adjustable stopspositioned in spaced relationship on said feed drum, means for indexingsaid feed drum to present a different stop in an operative positionduring each grinding cycle, a xed stop, and control means movablebetween said xed stop and an operative one of said adjustable stops andeffective to actuate said indexing means and said advancing means, thelatter being actuated in proportion to the movement of said controlmeans between said stops.

8. A feeding device according to claim 7 wherein said indexing meansincludes a downwardly biased push rod, a ratchet wheel connected to saidfeed drum, a pawl on said rod engaging said ratchet wheel, and saidcontrol means includes an element engageable with said push rod duringeach grinding cycle to move said rod against said biasing means to movesaid feed drum.

9. A feeding device for thread grinding machines comprising a work piecesupporting means, a constantly rotating grinding wheel, means foradvancing said grinding wheel toward said work piece supporting meansand into operative association with a work piece supported therebyduring each grinding cycle, a feed drum, a plurality of adjustable stopspositioned in spaced relationship on said feed drum, means for indexingsaid feed drum to present a different stop in an operative positionduring each grinding cycle, a fixed stop, a control rod,'a member onsaid control rod extending outwardly therefrom and movable between theoperative one of said adjustable stops and said fixed stop, said memberbeing engageable with said indexing means to actuate the latter duringeach grinding cycle, means on said control rod connected to saidgrinding wheel advancing means to rotate the latter and effect movementof said grinding wheel in proportion to movement of said control rod, apiston on the opposite end of said control rod, duid pressure means,means to direct said iiuid pressure against the bottom of said piston tomove said control rod upwardly and move said grinding wheel in adirection away from said work piece, and means for directing saidpressure means against the top of said piston to move said control roddownwardly to advance said grinding wheel into said work piece inaccordance with the movement of said control rod as limited by theelement thereon contacting said operative one of said adjustable stops.

l0. A feeding device according to claim 9 wherein said means foradvancing said grinding wheel includes a screw type spindle, a nutsecuredto said grinding wheel and rideable in a groove of said spindlewhereby rotation of said spindle causes movement of said grinding wheelaxially along the length of said spindle.

ll. A feeding device according to claim 9 including means to directpressure to said cylinder above said piston when the pressure at thebottom of `said piston reaches a predetermined amount.

l2. A feeding device according to claim 9 including pressure operablemeans to direct fluid pressure to the top of said piston.

13. A feeding device according to claim 9 wherein at least one of saidadjustable stops provides for a cycle of operation in which the grindingwheel is maintained out of contact with said work piece.

References Cited in the le of this patent UNITED STATES PATENTS

